Prognostic significance of myocardial salvage assessed by cardiovascular magnetic resonance in acute reperfused myocardial infarction

Abstract

Acute myocardial infarction is a major cause of disability and death worldwide. In patients with MI, the treatment of choice is timely and effective myocardial reperfusion using thombolytic therapy or primary percutaneous coronary intervention for reducing acute ischemic injury and limiting MI size. PCI is superior to fibrinolytic therapy when performed rapidly by expert teams but its effectiveness may be limited by delays in delivery, door-to-balloon time is a key indicator of quality of care, the Guidelines of the American College of Cardiology, the American Heart Association and the European Society of Cardiology recommend a treatment goal of 90 minutes or less for door-to-balloon time. Myocardial salvage assessment is the mechanism by which patients with acute myocardial infarction benefit from reperfusion therapies. To assess the efficacy of therapy, it is necessary to determine how much myocardium is salvaged by measuring the difference between AAR and FIS, the myocardial salvage index can be calculated as the proportion of salvaged AAR. Salvaged myocardium can be assessed by 99mTc-Sestamibi SPECT, angiography or MRI.

Angiographic assessment of AAR relies on the anatomical distribution of the coronary arteries. Three models have been proposed to be clinically useful to estimate the anatomic territory at risk of infarction. The simplest model is the Duke Jeopardy Score by which the coronary tree is divided into six segments. Calculation of salvage using angiographic requires quantification of FIS by other imaging modalities, as CMR. SPECT imaging for assessment of salvage myocardium require 2 separate perfusion studies as FIS imaging must be postponed at least 120 h as 99mTc-Sestamibi uptake performed at 48–72 h overestimates FIS. Optimal timing is probably after several weeks which is time consuming and leads to additional radiation exposure. MRI is preferred to other modalities for its higher temporal and spatial resolution without exposure to radiation or radioactive material with ability of evaluation of extra-cardiac structures and estimation of both AAR and FIS in single exam taking about 30 minutes. In our study, radiologists interpreted and analyzed the imaging data of 25 patients who met the inclusion criteria and performed CMR in MRI unit in Ain Shams University Educational Hospital 2-4 days post PCI.